1. Field of the Invention
This invention relates to a shaped fibrous article and a process for making the shaped fibrous article having a preselected configuration and thickness by a vacuum forming process and more particularly to a shaped fibrous article and the process for making the shaped fibrous article by a vacuum forming process in which a substantial portion of the fibers are oriented substantially parallel to the forming surface.
2. Description of the Prior Art
U.S. Pat. Nos. 2,539,767; 2,700,326; 3,028,911 and 3,442,757 disclose both methods and apparatus for forming filter elements from a fibrous slurry. In U.S. Pat. No. 2,539,767 a filter element with a graduated porosity is obtained by controlling the degree of vacuum and the length of time over which the vacuum is applied to the accreted fibers. U.S. Pat. No. 2,700,326 discloses a process for progressively elevating a shaped tube around the foraminous former to obtain a uniform accreted filter element. U.S. Pat. No. 3,442,757 discloses a process for positioning a cylindrical element over the former to control the density and size of the accreted filter. U.S. Pat. No. 3,028,911 suggests subjecting the forming tank to a pressure during the accretion of the fiber on the forming tube.
U.S. Pat. No. 1,859,325 discloses apparatus for making cylindrically shaped articles from paper pulp by accretion on the forming tube. The exterior surface of the accreted pulp element is pressed between two cylinders to remove additional water. U.S. Pat. No. 2,107,779 discloses a method and apparatus for producing fiber pipe insulation that includes a cylindrical mold having an outer foraminous surface. The mold is agitated and vibrated while a slurry of the mineral fiber and binder is introduced into the mold. The mold is thereafter rotated at a high speed to further extract water from the fibrous material deposited within the mold.
U.S. Pat. No. 2,101,921 discloses a method and apparatus for forming mineral wool insulation by moving a foraminous mandrel in a direction normal to its axis through a bath containing mineral fibers. When a layer of mineral fibers having desired thickness is deposited on the outer surface of the mandrel, the mandrel is moved into abutting relation with an inclined surface where the deposited fibers are compressed and shaped. Thereafter, while remaining on the mandrel the deposited fibers are dried in an oven.
U.S. Pat. No. 3,371,134 discloses a method for making a water laid sheet from a slurry that consists essentially of water, an inorganic wool and a clay. The water laid sheet is dried to remove the water and is fired at a temperature of between 1,000.degree. and 1,600.degree.F. to form a ceramic bond. U.S. Pat. Nos. 3,470,062 and 3,549,485 are also directed to a method of making water laid sheet from a slurry of inorganic wool and a clay and disclose additives such as alumina, starch, flocculents and de-flocculents.
There is a need for a simple and inexpensive process for making a mineral fiber insulation product and particularly pipe insulation having a substantial portion of the fiber oriented to provide the desired physical strength and insulating properties and does not require the elaborate external shaping apparatus or agitating and vibrating the mandrel during the accretion of the mineral fibers or shaping and drying the mineral fiber insulation in an oven while the insulation remains on the mandrel.